autotrace on

见《D33513-ORACLE9i Performance Tuning Vol1.pdf》14-24

SQL> set autotrace on
SQL> select employee_id from employees where rownum<10;

EMPLOYEE_ID
-----------
        100
        101
        102
        103
        104
        105
        106
        107
        108

已选择9行。

Execution Plan
----------------------------------------------------------
   0      SELECT STATEMENT ptimizer=CHOOSE (Cost=1 Card=9 Bytes=321)
   1    0   COUNT (STOPKEY)
   2    1     INDEX (FULL SCAN) OF 'EMP_EMP_ID_PK' (UNIQUE) (Cost=1 Ca
          rd=107 Bytes=321)

Statistics
----------------------------------------------------------
          7  recursive calls
          0  db block gets
          4  consistent gets
          0  physical reads
          0  redo size
        483  bytes sent via SQL*Net to client
        503  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          9  rows processed